


love me like my demons do

by towokuwusatsuwu



Category: Kamen Rider Build
Genre: Companionable Snark, Desk Sex, Explicit Sexual Content, Foreshadowing, Introspection, It's Not Paranoia If They're Really Out To Get You, Lab Sex, M/M, Mild Blood, Oral Sex, Pre-Canon, Rogue Episode One Spoilers, Sort of at least
Language: English
Status: Completed
Published: 2018-07-01
Updated: 2018-07-01
Packaged: 2019-05-31 19:57:34
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 7,205
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15126773
Author URL: https://archiveofourown.org/users/towokuwusatsuwu/pseuds/towokuwusatsuwu
Summary: Gentoku makes a deal with the devil and now he has to give the devil his due. That they do this on the desk of this ex-lover has nothing to do with anything else, of course.





	love me like my demons do

**Author's Note:**

  * For [gulpereel](https://archiveofourown.org/users/gulpereel/gifts).



The interior of the laboratory is quiet this late at night, the clock in the corner of a nearby computer screen showing the time as half past three in the morning. At a time like this, the lab should be empty and locked up for the evening, each employee at home in bed resting for the next day, the next experiment, the next step needed to grow ever closer to their goal. Even with the genius of Katsuragi Takumi on their side, they need to be prepared for each and every misstep that will come as they adapt to each change, each discovery.

By this logic, Himuro Gentoku should be at home in bed instead of skulking around the lab.

He knows he should be home, of course. Not only does he have his job in leading Faust forward, but Hotei’s mysterious death opened the door for Gentoku to take on the position of aid to the prime minister. Working with his father may not be particularly stimulating work, not compared to this, to Faust, to the organization he raised with his own hands and oversees each evening when his father thinks he has gone home, but the position affords him the luxuries he needs to guide his plan forward. He swore he would change the country for the better, and to do so, he needs to play every side of the field to his advantage.

Having a government job means no end to the red tape, and Gentoku needs his sleep so he can put on his political smile. So he can handle the other prime ministers when the meetings come, so he can fill out the necessary paperwork for each and every little movement of the Touto government. The drone of each day is maddening, threatening to drive him that much closer to insanity, but he must persevere for the better of Touto, and for Japan. When the walls come down, Gentoku will be the only person left with a true plan in place.

Tomorrow evening, he has a meeting with Nanba Juzaburo, the old man annoyingly insistent on knowing each discovery Katsuragi makes. He tracks their movement carefully and though Gentoku understands— the man is funneling so much money into their operation that he needs to prove Faust is worth the investment, worth the wait— he can never quite shake the way the hairs on the back of his neck stand on end. He trusts no one and nothing, not even his allies, and so this invasion of what feels like his personal and private space never settles well.

Again, logic would state Faust does not belong to him, not truly. He might have put together the necessary equipment, handling the financial side of their operation so Katsuragi can focus on the science, on the experiments and the results, but Gentoku knows he does not own Faust. No one can, not truly, and Faust would fall apart without Katsuragi here to make the necessary advancements forward. Just the same, Faust  _ feels _ like it belongs to him, and someone else butting into his affairs is upsetting.

The laboratory is one of the few places he finds peace these days. Going home to rest at the end of a long day more often than not ends with him pacing his apartment until he falls asleep, feeling more like a caged beast as the days drag on. He has to perfect his roles as both Night Rogue and as the prime minister’s aid, but that never makes it any easier. The stress is high in both places, threatening to suffocate him.

He could go to Katsuragi’s apartment, but the tenuous relationship between them had grown strained and cold on his end when he discovered Hotei’s lifeless body, when he agreed to work with Isurugi Soichi. He knows Katsuragi must have his suspicions, because a man so brilliant could hardly be so blind to such a thing, but there is nothing Gentoku can do. He needs all the hands he can get, and if Isurugi can offer him something, then he wants it.

If Isurugi can offer him the power to take the next step, Gentoku will seize that power gladly.

The sound of footsteps echoing off the walls of the hallway has Gentoku lifting his head, makes him aware of how numb his legs feel. Perched on the edge of Katsuragi’s desk with a stack of his paperwork in hand, he was willing to remain here and reread the gripping content of Katsuragi’s latest reports until morning had no one discovered him. He might not always understand the language Katsuragi uses, but he can piece together the words well enough.

“Who’s there?” He lets his voice grow as hostile as he wants until the words leaving his lips sound more like a guttural growl.

Anyone here this late deserves all the ire he can muster with what little energy he has left.

“Now, now, that’s not a very polite way to address your new partner!” The voice has him sighing, pinching the bridge of his nose. A moment passes and Isurugi appears at the top of the stairs, leaning against the railing. Even with the distance between them, Gentoku can almost sense the catlike smile on his face, smug, like he knows something no one else does. “What are you doing here so late, Gentoku? Shouldn’t you be home in bed at this hour?”

“It’s my duty to make sure I’m up to speed on all of Katsuragi’s research.” The lie comes easily and readily. Gentoku has been lying so often lately it’s become a second language of sorts for him. “Interesting of you to ask considering you’re also here at this hour.”

Isurugi laughs, and the sound bounces off the walls. “I couldn’t sleep and thought I’d come see what our dear Takumi has been working on. He’s such a bright boy, isn’t he?”

The question sets Gentoku’s teeth on edge but he ignores it, setting the files next to him, slipping off the desk. His legs threaten to buckle under him, protesting his sudden use of them, the weight on his tired joints. “Read his reports, then. They’re right here.”

He watches as Isurugi walks down the stairs, each step slow and measured, a sinuous roll of muscle under the pressed brown jacket, the neat slacks, the button-up. Though Gentoku knew precious little about Isurugi other than that the man had triggered the Skywall by touching Pandora’s Box, he can’t help but think something seems off about him. Research into his background uncovered a hospital stay following a hysteria that sent him running through the city. They had to pin him down just so they could sedate him.

This much, Gentoku can believe. Isurugi is unhinged behind that cheerful smile, the one that never quite reaches his dark brown eyes which look black in just the right lighting. This lighting, for instance, because when Isurugi joins him at the desk, his eyes are like black holes out in space, swallowing up everything around them, even light particles.

“His intelligence is so interesting to me.” Isurugi picks up the files, flips through them too quickly to read more than a few words at a time, though his eyes linger on the diagrams for long, long periods of time. The smile on his lips widens, becomes almost deranged. Or maybe Gentoku is merely too tired to deal with him right now.

“Katsuragi’s a genius,” Gentoku agrees, maneuvering around the man. If he had been anyone else, Gentoku might have fought him on lingering here at such a late hour with no one else here to keep an eye on him, but he knows that restraining Isurugi is already impossible.

A hand closes vice-like around his arm and he turns his head, his eyes fixed on the fingers gripping him through the fabric of his government uniform. When he raises his eyes, Isurugi is smiling at him, his head cocked to the side. “Where are you going, Gentoku?”

“I thought I might go home.” Gentoku keeps his tone light, conversational, and tries to ignore the way his skin crawls at Isurugi’s touch.

“But I wanted to talk to you about something. It’s difficult in the light of day, when there are so many people scampering around the laboratory. I wouldn’t want one of them to overhear.” Isurugi’s fingers twitch and Gentoku relents, taking a seat in a nearby chair. “Thank you! Such a polite man. You’re so busy and yet you’re making time to talk to me.”

The cheerful tone of Isurugi’s voice never fails to unsettle Gentoku, but something about it here in the dark seems almost menacing. He remembers comparing Isurugi to Mephistopheles in an errant remark, one that would help kickstart the partnership between the two of them, and the comparison has never felt more apt than it does right now with Isurugi staring at him with those dark eyes, smiling at him with a smile that feels like it should be fangs and blood instead of normal white teeth. Maybe Gentoku can only think so many charitable thoughts about a man he knows has killed, the proof of which was right before him (right beneath his shoe).

“What did you want to talk to me about?” Gentoku asks him. Better to get this over with as quickly as possible so he can return home rather than linger any longer.

Isurugi sets the files down and leans against the edge of Katsuragi’s desk, arms folded over his lean chest, and not for the first time Gentoku is struck by how tall this man is. His body is so long, and if Gentoku’s mouth goes a little dry at the thought, so be it. Unstable and dangerous that he may be, it is getting harder and harder to ignore that Isurugi is a handsome man.

“I believe we made a deal with each other,” Isurugi says.

Gentoku nods slowly. “Correct. I believe I compared it to making a deal with the devil.”

“Getting right to the point of the conversation. I like that about you. You’re very blunt.” Isurugi advances on him slowly and Gentoku thinks, in that moment, that sitting down was a mistake. He feels like a prey animal being stalked by a predator. “There are a lot of things I like about you, as it turns out. You impress me. It’s very rare that anyone is able to do that.”

“Thank you?” The compliment is bewildering at best.

Isurugi chuckles, leans over so that his hands rest on the arms of Gentoku’s chair, pinning him firmly in place. “Good manners. I like that. You know, I thought you were going to be something special when you stepped on your friend. Or was he more than a friend? You seem to have a tendency to get involved with people in your workplace, after all.”

“He was a friend.” The past is the past, and they had been nothing but acquaintances if Gentoku is being fair, when all was said and done. Acquaintances with too many differences and communication issues to be anything more ever again. “And stop saying such things.”

“Do you understand why I wanted to have this conversation in private?” Isurugi asks.

Gentoku sneers at him. “It’s very late. If there’s a point you’re trying to make, or something you’re trying to dance around or work up to, then stop. Tell me outright. This is tiring.”

“What a pity. I have such fun talking to you but you never want to talk to me.” Isurugi leans closer to him and Gentoku can smell his cologne, something he might have liked on another man, and something underneath that, dusty and vaguely metallic. What is that? “You are correct. We made a deal. Usually, you know, demons seal such deals with markings, or with offerings. But I thought we could seal our deal a little differently. You’re a politician now, aren’t you? So you understand the necessities of having such contracts made official.”

Before Gentoku can answer him properly, thrown by his terminology, thrown by his closeness and the dark glitter of his eyes, Isurugi catches him by the collar of his uniform, fingers folded beneath the fabric, brushing against the front of Gentoku’s throat. The touch is electric; he and Katsuragi have not touched in weeks now, and though Gentoku has beared the weight of this silence between them, the frustration has been getting to him. While he never had reason to doubt Katsuragi was on his side, the snide little voice in his head has been pointing out that this may not be so after all.

Sometimes when Katsuragi looks at him, there’s something in his eyes that’s just off.

“You aren’t saying anything.” Isurugi’s grip on his collar tightens and he jerks, and Gentoku’s body jolts forward at the motion.  _ Has he always been this strong out of suit? _ “It’s very difficult to discuss ways to seal a contract when the other person isn’t quite as responsive, Gentoku.”

Gentoku swallows hard and wonders if Isurugi can feel it against the backs of his fingers. “You want to seal the contract? We can do that. But I don’t know how you want to go about it.”

“Such an agreeable boy. You must be a very good politician, after all.” Isurugi lets him go, setting a hand on his shoulder, guiding him to lean back in his chair. “How long has it been since dear Takumi has touched you? I have my own estimations, but—”

“What are you implying?” Gentoku cuts him off, fingers gripping the arms of the chair.

Isurugi sighs and rolls his eyes, and the expression looks so  _ bratty, _ something about it so casual on him that Gentoku thinks, for just a moment, that maybe Isurugi isn’t who he thinks he is. “I’m not an idiot, Gentoku! Cute of you to think so, but I know what I see when I see it. How long?”

“I’m not answering that question.” He does his best to keep his voice steady, to not look away from Isurugi’s gaze. He will not waver or show weakness. “Your implications are annoying. And why are you asking such a thing in the first place?”

“Because you’re interesting to me.” Isurugi’s voice drops several octaves, low and throaty, and Gentoku’s gut clenches hard at the sound, his mouth dry. “Because I haven’t met a man like you before, and it’s exciting! I knew you were different from the others when you stepped on your friend’s body. You could have stepped over him, but you asserted then and there in front of me that you had what it takes to come this far, and go farther. It’s… An aphrodisiac of sorts for me.”

Gentoku’s lips part but no sound escapes them, his brain struggling to keep up with Isurugi’s outrageous claims and the horrible suggestion on the tip of his tongue. “You want…”

“Good boy. Now you’re getting it.” Isurugi shrugs out of his jacket, folding it neatly in half before setting it on the desk next to Katsuragi’s files. “To meet someone so different, so intriguing, so willing to do what it takes… Is it so wrong to want to experience that person?”

“You want to seal our contract with… W-with—” Gentoku can’t finish the sentence.

Isurugi smiles politely at him. “Is that really such a strange request from someone like me?”

He shouldn’t. He knows he shouldn’t. The man he once thought was just an astronaut assigned to help with Faust and the reformation of the country is hardly just that; he’s dangerous, deadly, willing to kill to get what he wants with even less scruples than Gentoku. There’s something about him that isn’t quite right, something about him that makes some instinct in the back of Gentoku’s mind go haywire, red alerts flashing through his brain so often around Isurugi it feels like a constant thrumming that only fades into the background when the man is not within immediate sight, and sometimes from just a phone call.

There’s no ignoring the way his cock twitches in interest, though. Gentoku would have thought he wasn’t interested in an older man like this, especially not someone like Isurugi, and yet… Maybe Katsuragi’s ignorance has created just the perfect storm to give Isurugi what he wants.

_ He waited for this, _ Gentoku tells himself.  _ He waited because he knew I’d be less likely to say no. _

“Fine.” The word comes out with the slightest quiver and Gentoku grips the arms of the chair so hard they tremble in his grasp as if threatening to break from the pressure.  _ No weakness. _

“What a good man.” Isurugi’s hands are on him then, fingers slipping beneath the edge of his uniform, popping the snaps as he goes down. “I’ve been waiting too long for this.”

A confirmation on Gentoku’s thoughts, then.

He isn’t normally content to lie back and let someone undress him even in his worst moments but something about his body refuses to let him move. Isurugi’s fingers are quick, dexterous,  _ experienced _ and he has his hands under the uniform in seconds. It’s almost comical to see his expression when he encounters the soft white fabric of Gentoku’s undershirt beneath, the way his eyes narrow for just a moment before he yanks Gentoku out of the chair.

“That’s just teasing,” he says, and Gentoku frowns at him.

“The undershirt is more comfortable, and the uniform is very scratchy inside,” he says, his face burning when Isurugi smiles at him,  _ coos _ at him, the bastard. “ _ What? _ ”

“You’re  _ cute, _ Gentoku. I appreciate the contrast very much, I’ll have you know.” Isurugi pushes the uniform off of his shoulders, eyes raking over Gentoku’s upper body, hands running down his bare arms. “Ah, but maybe it’s not so bad. I suppose it’s like unwrapping a present and going slowly so you can savor the moment.”

Gentoku shoves Isurugi back, his arms crawling with goosebumps. “You’re too slow at this,” he snaps, pulling the undershirt over his head, tossing it aside, not caring what it hurts in the process, if anything breaks. Katsuragi can clean it up in the morning when he shows. “How do you get anything done when you drag everything out?” The uniform pants come off easily enough after, getting tangled around his feet just a little until he manages to kick them and his shoes off. “I don’t have time for—”

Isurugi shoves him back in the chair so hard it goes skittering back several feet and Gentoku grabs the arms of it to stabilize himself, his heart beating staccato off of his ribs, and had Isurugi seemed inhumanly fast just now? Is that normal, that kind of speed?

“I’ll do the rest myself.” Isurugi drops to his knees, smoothing his hands up Gentoku’s thighs, fingers digging in just a little where they meet his boxers. “I would’ve thought you’d be more muscular under all of the clothing. Your build lied to me.”

Gentoku tries to surge out of the chair. “Shut up—”

Isurugi shoves him back, and the chair leans back a little too far, almost far enough to fall. “Stop being such a child. If I didn’t find such aspects of you attractive, I wouldn’t bother with this.”

The manhandling makes Gentoku that much more aware of the fact the two of them are alone in this dark, quiet space. It feels like being trapped in a cage with a predatory animal, and that shouldn’t make his dick harder, shouldn’t make heat pool in the pit of his stomach, shouldn’t make him all the more willing to go through with what Isurugi wants. But those hands are still on his thighs and Isurugi smirks up at him, showing teeth.

“All right,” he says, and it takes entirely too much effort. “Go ahead.”

“Good choice!” Isurugi’s hands shift under him, gripping the waistband of his boxers and yanking them down hard enough that the fabric tears. The sound is painfully loud in the lab, echoing off of the walls. “Ah, you’re already getting excited for me. That’s good. I like that.”

Gentoku isn’t fully hard just yet but Isurugi doesn’t seem to mind this. He wraps a hand around him, callused fingers stroking him slowly and gently, coaxing him to full hardness. It’s been so long since anyone has touched him— not  _ that _ long but it feels like ages when he and Katsuragi used to be unable to keep their hands off of each other until recently— that it doesn’t take much. He would almost be embarrassed about that if he could think about it.

Having Isurugi touch his cock makes it hard to think at all, as it turns out. Those dark eyes are fixed between his legs, studying his reactions while he strokes Gentoku until he’s achingly hard, until the tip of his cock beads with pre-come. He smiles then, a small little expression that makes Gentoku’s breath hitch, before he leans forward to lick the pre-come away.

“That’s the reaction I wanted.” Isurugi’s voice has dropped low once again, an almost-purr that make Gentoku’s fingers grip the chair arms this time, not out of anger but as an anchor. “You’re fine with my mouth, I assume? I don’t know your particular tastes but that seems to be an across the board interest for most men your age.”

The way he talks is off, distant, like he’s not a part of the demographic he’s talking about, but Gentoku’s brain only barely makes the connection and then it’s gone again. He’s hot, stifling hot even though Isurugi has hardly touched him, and he can see the flush spreading down his chest even in the dim lighting. Isurugi waits patiently for his response, pumping Gentoku slowly but surely, his eyes fixed on Gentoku’s face. Just the same, his little smirk reassures Gentoku that he knows he’s not going to be denied this because he knows Gentoku wants it just as much as he wants to do it. It’s unnerving that Gentoku can read this in his face.

Just how much time have the two of them been spending together these days?

“Please,” he manages, and Isurugi beams up at him.

“Polite! Such manners. Your father must have raised you very well.” Isurugi wets his lips and it looks predatory. “Very well, Gentoku. Lean back and relax.”

That seems impossible to do but Gentoku does his best, slouching in the chair, alarmed when Isurugi lets him go just to hook his hands in the back of Gentoku’s knees to pull him forward a little. His legs splay open wider to accommodate Isurugi kneeling between them and he feels suddenly much too vulnerable for this. Then Isurugi takes his cock back in hand, wrapping his lips around just the tip, and Gentoku stops thinking so much.

Isurugi  _ does _ have experience, as it turns out. His tongue laves the head of Gentoku’s cock, warm and hot and slick as he wraps his lips tighter around him. Spit makes it easier to suck him off, wetting his cock and decreasing the friction but not so much that it isn’t pleasurable still, and maybe he gets off on this just a little, too, Isurugi drooling on his cock like this. Not that he’s ever going to admit that to anyone except himself, but Gentoku finds it almost easy to let go, to let Isurugi do what he wants as long as it feels this good.

He bobs his head at a slow and even pace, slurping around Gentoku’s cock as he goes down, tongue stroking up the sides and over the head as he goes. One hand is still wrapped around the base of Gentoku’s cock, holding him in place until Isurugi lets him go to swallow him all the way down. It’s sudden and jarring and Gentoku yelps a little, gripping the chair arms tighter, head falling back at the heavenly tightness around him, the pressure when Isurugi swallows.

“Isurugi,” Gentoku chokes out. His hand moves of its own accord, knotting in Isurugi’s hair, mussing the carefully crushed and combed locks, twisting them between his fingers.

Isurugi looks up at him with his mouth still around Gentoku’s cock and it’s somehow very lewd, much more so than Gentoku would have expected. It doesn’t help that he doesn’t still his movements, still bobbing his head if just a little slower, still sliding his tongue all over Gentoku’s cock until it’s hard to think straight, hard to keep his focus.

He was going to say something, but Gentoku gives up and guides Isurugi’s movements instead, surprised the man lets him. Of course, he soon bucks the control entirely and bobs his head faster, swallowing Gentoku down again, slurping around him so noisily Gentoku is almost embarrassed by the wet hot sounds.

“You taste better than expected,” Isurugi informs him, letting him go with a wet pop, his lips bruised a darker color now. There’s a slight flush in his cheeks but he still looks somehow as suave and in control as ever even though that doesn’t seem possible. “And I’ve got quite the memory bank to compare it to, I’m sure you can imagine.”

Gentoku wrinkles his nose at the words. “Do we have to talk about your sex life right now?”

“I suppose not. I was just trying to give you a compliment. Don’t be so ungrateful.” Isurugi grips his cock again, stroking him with just his hand. The spit means every pump of his fist sounds sticky and Gentoku squirms at the sensation. “It’s not easy for me to kneel on the ground like this with my joints. Are you enjoying yourself? You look like you are.”

“Y-yes.” Gentoku inhales sharply when Isurugi twists his wrist just a little. “I am.”

Isurugi looks pleased by this information, taking Gentoku back into his mouth, making direct eye contact that Gentoku has to look away from, too overwhelmed to continue looking at him like this. It’s strange enough to be sitting naked in a chair with his dick down the throat of some old man he only barely knew of a few months ago in front of all of Katsuragi’s hard work, but something about that last bit makes it better. Makes the sensations that much more, makes the pleasure tighten Gentoku’s stomach that much more. It  _ should _ be here, of all places.

When Isurugi hums quietly around him, Gentoku’s hips buck, his muscles tensing at the vibrations around his cock. He’s already fairly close to an orgasm and the vibrating only pushes him closer to that threshold until the muscles in his thighs tremble around Isurugi’s shoulders.

“No, no.” Isurugi pulls off of him again and Gentoku bites back a curse, slamming his head back into the headrest of the chair. “Now, don’t throw a tantrum. I have every intention of making sure you come, but not like this. That would be one-sided, wouldn’t it?”

“I don’t follow.” The words come out as a low growl, more hostile than Gentoku intends.

Isurugi stands and Gentoku’s attention is brought to the front of his hips, the bulge beneath the dark brown pants that match his jacket. Balls deep in the man’s throat and he hadn’t thought about his pleasure once, not when he was so close to completion himself. He watches Isurugi unbuckle his belt and unfasten his pants, making a disgusted noise when his boxers turn out to be some obnoxious and colorful pattern.

“Don’t mock my fashion sense.” Isurugi pulls the fabric of his fly open wide, reaching up to unbutton his shirt. “Like I said, it would be one-sided to do it that way. I’d rather do it differently.”

Gentoku tells himself to relax even as tension tightens his muscles again. “What do you mean?”

“Not that I don’t enjoy oral sex, but sucking you off gave me an idea of just how large you were. Definitely doesn’t fit the rest of your frame.” Isurugi steps smoothly back when Gentoku aims a kick at him, nonplussed by the gesture. “I can take you, is what I mean. And it would be quite enjoyable for me. So you’ll lie back and let me ride you.”

“I don’t know about you, but I don’t exactly keep lubricant on my person.” Gentoku scans the room, not sure if he wants to go rifling through Katsuragi’s drawers to see if he still does or not. Either he keeps it because he hasn’t had time to throw it away, or he’s keeping it for another person, and neither situation is ideal to think about right now.

Isurugi pats him on the top of the head, condescension oozing from him. “Do you think I came here unprepared? I was planning this, don’t worry. I have some in my jacket pocket.”

“That’s… I don’t want to think about that,” Gentoku tells him.

“You’re an  _ adult, _ Gentoku, surely you understand the merits of always being prepared. Takumi used to keep some in one of his drawers, did he not?” Isurugi laughs when Gentoku’s eyes widen up at him, his mouth falling open, because how can he possibly  _ know _ these things? “Besides, the alternative was not being prepared, and that might have been very painful. Pain doesn’t bother me so much as you’d expect, but I’m sure the chafing would hurt you.”

“Who the hell even  _ are _ you?” Gentoku demands.

The question brings about a deadly silence and he stares up at Isurugi, not willing to look away this time as the man looks down at him, considering even as he shrugs out of his shirt. He isn’t in bad shape for a man his age, though Gentoku has never gone for older men, not in a situation like this one. Isurugi doesn’t answer him as he eases his pants down his hips, kicks them away carelessly and slips his boxers down as well. He’s achingly hard, larger than Gentoku would have expected if he gave any thought to it at all.

“I’m the devil you made your deal with,” Isurugi finally says. “Now, get my jacket.”

The creaking of wood behind him catches Gentoku’s attention but he refuses to turn around, fumbling with Isurugi’s jacket, finding the bottle of lubricant in the pocket. The protective seal has been broken and some of it is missing from the bottle; Gentoku decides quickly he doesn’t want to think about why Isurugi might have broken the seal or who he was using it with if anyone at all. He might have been using it on his own. Gentoku doesn’t want to think about that either.

When he turns around, he almost drops the bottle. Isurugi has arranged himself across Katsuragi’s desk, having pushed all of his research supplies to the side. Everything is messy; the computer keyboard has been perched on top of the monitor for space, papers slanted off in the wrong directions. Isurugi smirks at him and spreads his arms, and Gentoku wonders idly if Isurugi knows how viciously glad he is to see Katsuragi’s workspace disturbed.

He’ll notice. He’s not the kind of person not to notice when his things have been touched.

“Comfortable?” Gentoku asks him, coming to stand between his spread legs. It’s an echo of their earlier position, though Gentoku is standing and not on his knees. He won’t go on his knees, either, not for Isurugi.

Isurugi smirks up at him, braces a foot on the edge of the desk, spreading himself so wide that it’s painfully lewd and Gentoku doesn’t understand how he can be flexible enough to do this at his age. “Quite. This is only so I can watch your face while you open me up.”

“Don’t say things like that,” Gentoku mutters, popping the cap on the bottle.

The lubricant is water-based, slick enough on his fingers and he has the consideration just this once to rub it between his fingers just to warm it a bit. He’s well aware that Isurugi’s eyes are boring into him while he does this but he determinedly doesn’t look at him, shifting forward just enough, pressing a hand under Isurugi’s thigh to spread him just a little wider. This is not what he thought the two of them would be doing together when they agreed to work together.

But he made this deal, and Gentoku is a man who sees things through.

His fingers slip under Isurugi’s balls, stroking over his perineum for just a moment before he traces them around Isurugi’s hole. The man sighs and tips his head back, and Gentoku glances up at him, watching his expression change as he slicks over his hole before trying to press one inside of him. It goes in easy and Gentoku bites back a laugh at just  _ how _ easy, opting to start with two instead. Isurugi takes them both far easier than Gentoku would have expected, shifting so he sinks down on them just a little, pulling them in to the second knuckle.

“Don’t be shy, Gentoku,” Isurugi rasps even as his inner muscles tighten around Gentoku’s fingers. “I told you, I’m experienced. I can take whatever you dole out.”

He opens up easily even as his muscles tense and squeeze around Gentoku’s fingers, and Gentoku thinks for a moment he must be doing it on purpose, maybe teasing him with the promise of what he can do. Because when Gentoku works his fingers in and out, slowly at first just to be more considerate than Isurugi seems to need and then faster and with a little more force, all he does is moan and grip Gentoku’s shoulder hard enough that there will likely be some kind of bruise there in the morning, something to mark the occasion.

When Isurugi makes a frustrated noise, Gentoku gives him another finger, curling them against the front of his hole, shuddering when Isurugi groans and clamps down hard around his fingers. The man’s cock is hard, untouched and throbbing so Gentoku takes pity on him and wraps a hand around him, feeling the pulse against his palm while he jerks him off.

Isurugi’s squeezes his shoulder hard and Gentoku looks up at him, his face flushed and his pupils so dilated that, in this darkness, Gentoku can’t see the brown of his eyes anymore. Just blackness. “Switch places with me.”

It takes a little work to get the position just right, and Gentoku ends up dragging the desk away from the wall just a little to give them more space to work with, but they still have to use it longways so Gentoku doesn’t end up half-hanging off of it. The minute he’s sat on the desk, Isurugi climbs on top of him, straddling his hips, and Gentoku almost wants to snark that he’s not complaining about his joints so much anymore even though the wood has to be rough on him. Instead, he grips Isurugi’s hips, helping him get situated, almost admiring the muscle he can feel there even though Isurugi has never given him the impression he was built like this.

“Now lay back and relax for me.” Isurugi presses his hands down on Gentoku’s chest, pushing him down until his shoulder blades are against the wood. “I can do the rest on my own.”

Isurugi uses the rest of the lube on Gentoku’s cock, wrapping a slick hand around him, stroking him a few times to spread it evenly. Then he wraps a hand around the base, shifts his hips back, and sinks down in one slow, continuous motion that has Gentoku’s eyes nearly rolling into the back of his head. The sudden heat and tightness just keeps going, sucking him in centimeter by centimeter, almost pushing him into an orgasm though Isurugi hasn’t done anything yet.

“I have to say,” Isurugi says, his voice choked and a little husky, “your build might have been designed to trick me but this doesn’t disappoint at all. You feel just as good as I thought you would.”

The words are revolting but Gentoku only bucks his hips up just a little, impatient with the sudden stop, certain that Isurugi of all people wouldn’t need time to stretch around him. The movement jostles a moan out of the older man and Gentoku’s breath strains at the sound, the way that Isurugi rocks down against his hips. Then he plants his hands on Gentoku’s chest— for balance but it  _ almost _ feels like being held down— and rides him.

There’s something hypnotic about the way Isurugi’s hips rise and fall, the little rolling motions, the way his muscles flex beneath his skin. Gentoku is a little mesmerized and a lot turned on, his breath already ragged, hands settling on Isurugi’s hips before squeezing tight, his nails biting into Isurugi’s skin that he might be leaving marks of his own. If Isurugi minds, he doesn’t say so. Instead, he tips his head back, lips parted, little sighs and moans slipping past every few thrusts or so, a testament to how much he’s enjoying himself.

It’s been too long for Gentoku, the urge to just turn the tables so he can fuck Isurugi down against the wood until it strains and creaks and even  _ breaks _ pulsing through his body like a living thing, like a separate entity crawling beneath his skin. But there’s something about this— being held down, almost being used like this— that appeals to him. The position isn’t so bad, not with Isurugi’s movements, slow and seductive, almost vaguely serpentine.

Isurugi’s inner muscles tighten around his cock and Gentoku groans, head thumping back against the desk hard, hard enough to hurt, to do something about that impulse inside of him. He doesn’t want to take over, not really, not now. It’s been too long for him and there’s something satisfying about having to just lie here and let Isurugi do everything for him.

Maybe it’s less about him being used, and using Isurugi for this pleasure. Maybe the two of them are just using each other.  _ That _ has a ring of sincerity to it.

Isurugi’s fingers dig into his shoulders, his hips coming down particularly hard against Gentoku’s. “You’ve got a look in your eyes like you want to do something.”

“Maybe.” Gentoku’s grip tightens on Isurugi’s hips and when Isurugi rises and comes down again, Gentoku’s hips arch up, the impact delightful, the response even better. Isurugi chokes on a groan, eyes squeezing shut. “That’s good enough for me.”

“You really are an interesting human, you know that? The most interesting I’ve ever met.” And Isurugi leans down to kiss him, all tongue and lips and teeth.

_ Human? Did he say human? _

Isurugi’s kisses are bruising in intensity and Gentoku licks the taste of his moans out of his mouth, revels in the flavor, the sloppiness of it all. There’s something nice about how dirty this is, a nasty fuck in the Faust laboratory on top of the desk of the only man Gentoku had ever lo— No, no use thinking like that. It’s good because Gentoku is so used to nice and clean and neat things, has had a life built on privilege and propriety that this feels taboo and exciting.

He pulls Isurugi’s lips between his teeth and doesn’t even realize how hard he’s bitten down until he tastes the copper tang of blood on his tongue, sees the way Isurugi looks down at him, not upset but surprised and delighted all at once. He wipes a swathe of spit-diluted blood away with his fingers, rolling his hips down against Gentoku’s as he looks at his fingers.

Then he smears the blood across Gentoku’s mouth until Gentoku bites down on his fingers, too.

When he can feel his orgasm nearing again, he reaches between their bodies because this is a deal, a seal to their contract. That’s what he tells himself as he wraps his fingers around Isurugi’s cock, jerks it in time with the rise and fall of his hips, that he just wants to complete this properly and not because he wants to see the look on Isurugi’s face when he comes. He definitely does not receive a pang of satisfaction at the way Isurugi’s face contorts, the slight way his lips tip up at the corners, the way he tightens around Gentoku so much it almost hurts.

It’s enough to pull Gentoku down over the edge, crashing with him, the desk creaking dangerously beneath him as their bodies jerk and shudder in tandem with one another.

Isurugi lifts himself off of Gentoku, wincing as he slides off of the desk. “Well, I think that satisfies this agreement, don’t you? Well worth the wait in my opinion.”

“It was satisfactory.” Complimenting Isurugi feels like a mistake and when the man laughs at him, Gentoku only rolls his eyes. “Are we done here?”

“You’re so cold. I wonder what it is that Takumi saw in you.” Isurugi smirks at him when Gentoku grabs for the man’s jacket, throwing it at him as hard as he can. Instead, of course, Isurugi catches it, swings it around to drape over his bare shoulders. “Now, now, there’s no reason for that. I was only teasing you. You shouldn’t be so sensitive at your age.”

Gentoku sneers at him as he collects his clothing, only slightly wobbly on his feet, his knees still a tad unsteady from the force of the orgasm. “Should you be fucking people in labs at yours?”

“I suppose that’s fair. I suppose I’ll have to tell anyone who asks that I got into a little scuffle on the way home tonight.” Isurugi touches his lip again, studies his fingers. “Not even in my wildest fantasies did I think you’d let go even a little.”

“What does that even mean?” Gentoku demands.

Isurugi laughs, throws his head back, the sound echoing in the laboratory. “Don’t worry about it! It’s a compliment, anyway, not an insult. And yes, we’re done here. It’s up to you if you want to clean up the lab, you know I don’t bother with such things.”

Gentoku looks over the desk— Katsuragi’s desk— and turns away. “He can handle that himself.”

“That’s the spirit.” Isurugi steals another kiss before Gentoku can even process he’s near again, his lips still tasting faintly of blood. “Now go home and sleep. You’ll need it.”

It might be sleep deprivation that has Gentoku nodding and following along even though he has no reason to do so, no reason to listen to anything Isurugi has to say. Though he supposes it isn’t so bad, considering he was willing to let the man convince him to fuck in his ex-lover’s workspace. He might even let Isurugi convince him to do it again, and again, if Isurugi is so interested in him, if all of the words that flowed from his mouth ring true. It might almost be worth the stranger aspects of him.

Still, one thought lingers in the back of his mind, not quite letting him have any peace from this situation. It was probably just a slip of the tongue, and Isurugi is known to say strange things, but…

_ Did he say human? _


End file.
